UK citizens will be carrying high-tech "biometric" smart passports within four years, it has emerged.

And the planned new passports will complement David Blunkett's proposed "entitlement" ID card, creating a revolutionary multi-use format, the chief executive of the UK Passport Service told Computing Magazine.

Bernard Herdan outlined plans to create a 21st century passport, each containing an ultra-slim microchip, could hold digital images of the holder's face, as well scans of the iris of their eye and a full set of fingerprints."This is about allowing people to assert their own identity, preventing fraud and stopping identity theft. This is not about Big Brother," he said.

The new technology is already being used to cut out asylum fraud and keep tabs on refugees and the Treasury is likely to be keen on a scheme that could cut the expected £1 billion cost of a national ID card with a multi-function credential doubling as a smart passport.

"That's the direction we are going in and it chimes with the entitlement card. Our advice is that if you want a very secure identity, a database linked to a biometric system is the way to go, but it's up to the government to decide," said Herdan.